Neovascularization is a key regulatory process in fetal growth and development, providing nutrients and oxygen to tissues. Alterations within this process can lead to vascular abnormalities and impaired tissue development. Although a great deal is known regarding the interaction of factors promoting growth and development of the pulmonary vasculature, nothing is known regarding the molecular mechanisms that may counteract these stimuli. Accordingly the overall goals of this proposal are to determine, at a molecular level for the first time, the role of one putative negative modulator of lung vascular growth. I chose to focus on Endothelial monocyte activating polypeptide (EMAP) II as a candidate negative modulator because we recently identified a novel role for this cytokine as an anti-angiogenic factor in tumor vascular development and I now have preliminary data indicating that it may play a key role in negatively modulating angiogenesis within the developing mouse lung. I hypothesize that EMAP II is an important negative- regulator in the physiologic development and neovascularization of the lung. The specific aims of this project are: 1) To define the temporo- spatial expression of EMAP II in the embryonic mouse lung, 2) To determine the mechanism by which EMAP II inhibits lung vascular development, and 3) To determine the molecular basis by which EMAP II, an anti-angiogenic factor, inhibits vascular endothelial cell growth by analyzing the effect of exogenous EMAP II on cell proliferation, and cell cycle events. These proposed studies will determine whether EMPA II is an important negative regulator in lung development and neovascularization and will determine the effect of abrogation and overexpression. Based on this information, novel approaches to the clinical treatment of lung regeneration after ischemia-reperfusion injury, chronic lung damage and lung transplantation may be identified.